Lack of understanding of basic stem cell mechanisms limits current therapeutic approaches. In this renewal application, we will focus on the use of c-kit* cardiac progenitor cells (CPCs) to protect the heart against post-myocardial infarction (Ml) remodeling and heart failure (HF). The overall goal is to elucidate the molecular mechanisms that regulate the properties of CPCs and to evaluate the therapeutic utility of enhancing CPC function in order to optimize cardiac repair. Four closely inter-related and inter-dependent Projects will address different facets of this theme. Project 1 (Belli) will elucidate the role of CO and NO in regulating CPC function and therapeutic efficacy. The central hypothesis is that these gases are key determinants of CPC competence and that augmenting their levels will dramatically enhance CPC-mediated cardiac repair. Project 2 (Prabhu) will illuminate the deleterious effects of TNF on CPC competence and reparative ability. This project will test the hypothesis that differential TNF signaling via TNFR1, TNFR2, and NF-KB plays a critical role in determining adrenergic versus cardiomyogenic fate and, consequently, the reparative capacity of CPCs following Ml. Project 3 (Jones) will examine the role of protein 0-GlcNAcylation in modulating the fundamental properties of CPCs and will test the hypothesis that the 0-GlcNAc alarm signal plays a critical role in regulating CPC proliferation, survival, differentiation, and paracrine function. Project 4 (Bhatnagar) will determine how diabetes affects CPC-mediated myocardial repair and how CPC therapy can be optimized for the diabetic heart. The central hypothesis is that diabetes undermines CPC competence by inducing insulin resistance. Thus, all four Projects focus cohesively on CPCs. These Projects will be supported by four Cores that will provide expertise in mouse surgery, cell transplantation, CPC culture and phenotyping, pathology, flow cytometry, and cell sorting. This highly-focused PPG will be led by investigators who have collaborated productively for many years. Their long history of collaboration has resulted in closely integrated Projects that are ideally suited for a PPG. These will be the first studies to examine the role of CO and NO, TNF, 0-GlcNAcylation, and type 2 diabetes on CPC function: consequently, the results will be entirely new and will advance our understanding of CPC biology. In addition, these studies may lay the groundwork for new translational investigations of CPC therapy in patients with HF. Since we have already initiated the first-in-humans clinical trial of unmodified CPCs in patients with HF, we are well positioned to rapidly translate anv insights derived from this Program into new clinical investigations.